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<title>CMSIS-DSP: Frequency Bin Example</title>
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<div class="title">Frequency Bin Example<div class="ingroups"><a class="el" href="group__groupExamples.html">Examples</a></div></div>  </div>
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<dl class="section user"><dt>Description</dt><dd></dd></dl>
<dl class="section user"><dt></dt><dd>Demonstrates the calculation of the maximum energy bin in the frequency domain of the input signal with the use of Complex FFT, Complex Magnitude, and Maximum functions.</dd></dl>
<dl class="section user"><dt>Algorithm:</dt><dd></dd></dl>
<dl class="section user"><dt></dt><dd>The input test signal contains a 10 kHz signal with uniformly distributed white noise. Calculating the FFT of the input signal will give us the maximum energy of the bin corresponding to the input frequency of 10 kHz.</dd></dl>
<dl class="section user"><dt>Block Diagram:</dt><dd><div class="image">
<img src="FFTBin.gif" alt="FFTBin.gif"/>
<div class="caption">
Block Diagram</div></div>
</dd></dl>
<dl class="section user"><dt></dt><dd>The figure below shows the time domain signal of 10 kHz signal with uniformly distributed white noise, and the next figure shows the input in the frequency domain. The bin with maximum energy corresponds to 10 kHz signal. </dd></dl>
<dl class="section user"><dt></dt><dd><div class="image">
<img src="FFTBinInput.gif" alt="FFTBinInput.gif"/>
<div class="caption">
Input signal in Time domain</div></div>
<div class="image">
<img src="FFTBinOutput.gif" alt="FFTBinOutput.gif"/>
<div class="caption">
Input signal in Frequency domain</div></div>
 </dd></dl>
<dl class="section user"><dt>Variables Description:</dt><dd></dd></dl>
<dl class="section user"><dt></dt><dd><ul>
<li><code>testInput_f32_10khz</code> points to the input data </li>
<li><code>testOutput</code> points to the output data </li>
<li><code>fftSize</code> length of FFT </li>
<li><code>ifftFlag</code> flag for the selection of CFFT/CIFFT </li>
<li><code>doBitReverse</code> Flag for selection of normal order or bit reversed order </li>
<li><code>refIndex</code> reference index value at which maximum energy of bin ocuurs </li>
<li><code>testIndex</code> calculated index value at which maximum energy of bin ocuurs</li>
</ul>
</dd></dl>
<dl class="section user"><dt>CMSIS DSP Software Library Functions Used:</dt><dd></dd></dl>
<dl class="section user"><dt></dt><dd><ul>
<li><a class="el" href="group__ComplexFFT.html#gade0f9c4ff157b6b9c72a1eafd86ebf80" title="Processing function for the floating-point complex FFT. ">arm_cfft_f32()</a></li>
<li><a class="el" href="group__cmplx__mag.html#gaba4e0eff7816fe80d01121fb4cf6c6bc" title="Floating-point complex magnitude. ">arm_cmplx_mag_f32()</a></li>
<li><a class="el" href="group__Max.html#gad1eabd31544fe59c414d9ce5bd0cc151" title="Maximum value of a floating-point vector. ">arm_max_f32()</a></li>
</ul>
</dd></dl>
<p><b> Refer </b> <a class="el" href="arm_fft_bin_example_f32_8c-example.html">arm_fft_bin_example_f32.c</a> </p>
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